JP3434122B2 - Automatic seam welding line copying machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic seam welding line copying apparatus, and more particularly to a seam welding method in which a peripheral portion of a fuel tank is sandwiched between a pair of upper and lower electrode wheels to perform seam welding. The present invention relates to an automatic copying apparatus that corrects a welding trajectory of an electrode wheel at a peripheral portion of a fuel tank by horizontally turning the fuel tank while supporting the fuel tank in a no-load floating state in two orthogonal horizontal directions. . [0002] As shown in FIG. 8, a fuel tank 2 comprises an upper half 2a and a lower half 2b formed by a sheet metal press. To manufacture the fuel tank 2, these upper halves 2a
And the lower half 2b are overlapped with each other, and the mutually overlapping peripheral flange portions 4 are temporarily fixed by spot welding at a plurality of positions, and the thus-formed integral fuel tank 2 is set on a special jig 6, and the fuel tank 2 Press the upper surface of the
It is supported on the mold arm 10. The C-shaped arm 10 includes the fixed wall 1
It is supported by the tip of a horizontally bendable arm called an iron man 14 extending in the horizontal direction from 2. The iron man 14 has at least two arm members 1
Reference numerals 4a and 14b extend horizontally via a hinge 16 having a vertical axis, and support the fuel tank 2 movably in a horizontal arbitrary direction with a light force. Exclusive jig 6 and clamp 8
Are C-arms 10 at free rotation axes 18 and 20, respectively.
The copying jig 22 is attached to the lower free rotation shaft 18. The copying jig 22 has a plurality of guided pins 26 protruding from the lower surface of a small plate 24 having a shape similar to a reduced and similar planar shape of the fuel tank 2, and one of the guided pins 26 supports the support arm 28. The guide is linearly guided by a rail 32 fixed to the fixed wall 30 through the intermediary. Each guided pin 26 is arranged in alignment with a vertical line passing through the center of curvature of the corner of the fuel tank 2 as shown in FIG. The illustrated fuel tank 2 has four corner portions R1 to R4, and a total of four guided pins 26 (26a to 26d) protrude from the lower surface of the small plate 24 corresponding to these corner portions R1 to R4. I have. As shown in FIG. 10 (A), the rail 32 has a trough-like shape with a rectangular cross section at the rear end and closed at the front end. 3
4 and 36 are cut out so that the guided pin 26 enters the rail 32 from one of these two inlets 34 and 36. In the lower frame of entrances 34 and 36, FIG.
As shown in (C), a stopper pin 40 whose lower part is supported by a spring 38 and whose upper part is formed in a slope is provided so as to be able to move up and down, so that the guided pin 26 once inside the rail 32 does not go outside. It has become. A stopper block 42 is fixedly provided on the inner surface of one side of the front end of the rail 32, as shown in FIG. 10B. When the small plate 24 is turned 90 ° in the direction of the arrow by the feeding action of the electrode wheel 46 in this state, the notch 27 of the guided pin 26 faces the stopper block 42 and the passage of the guided pin 26 is stopped. It is now acceptable. [0005] A conventional seam welding method for the fuel tank 2 is as follows.
With the fuel tank 2 supported as described above, the peripheral flange portion 4 of the fuel tank 2 is sandwiched between a pair of upper and lower electrode wheels 46 of the seam welding machine, and the two electrode wheels 46 are rotated while rotating the electrode wheel 46. The peripheral flange portions 4 that have been in contact with each other by being energized in between have been resistance-welded. When the straight portion L1 of the peripheral flange portion 4 is seam-welded as shown in FIG. 9, the fuel tank 2 moves forward without changing its posture. At this time, the guided pin 26a moves inside the rail 32 toward the front end. However, when the electrode wheel 46 reaches the corner portion R1 of the peripheral flange portion 4, the movement of the guided pin 26 is prevented by the stopper block 42, and therefore, the fuel tank 2 is moved around the electrode pin 46 around the guided pin 26. It rotates in the direction of the arrow due to the horizontal rotational moment generated by the feed action. When the electrode wheel 46 has finished turning around the corner portion R1, that is, when the fuel tank 2 has been rotated by 90 °, another guided pin 26b enters the rail 32 from the inlet 36 and the peripheral flange portion 4 of the fuel tank 2 Is seam-welded by the electrode wheel 46 in the same manner as described above. When the linear portion L2 is welded, the corner portion R2 is subsequently seam-welded by the electrode wheel 46, and then the guided pin 26c is connected to the inlet 34.
The linear portion L3 enters the rail 32 from above and is seam-welded by the electrode wheel 46. In a conventional automatic seam welding line copying apparatus, a dedicated jig 6 is provided for each type of the fuel tank 2.
Since the profiling jig 22 is required, the dedicated jig 6 and the profiling jig 22 must be newly manufactured every time the shape of the fuel tank 2 is changed. Long production time was required. Therefore, the fuel tank 2 is supported by a robot without using the copying jig 22, and the fuel tank 2 is controlled to be fed in accordance with the progress of the seam welding by the electrode wheel 46, so that the peripheral flange 4 of the fuel tank 2 is controlled. A study has been made to obtain the desired welding line (see Japanese Patent Application Laid-Open No. Hei 7-241684). However, it is extremely difficult to accurately grasp the progress of seam welding by the electrode wheel 46 in real time. This corresponds to the peripheral flange portion 4 of the fuel tank 2.
The thickness of the electrode ring 46 is varied, the peripheral flange portion 4 is softened by energization between the electrode wheels 46, and
6, the rotation speed of the electrode wheel 46 running on the peripheral flange 4 does not match the actual feed distance of the peripheral flange 4, and the feed distance fluctuates minutely and momentarily. is there. The feed control of the fuel tank 2 by the robot may be performed by a teaching method or a feedback control method in which the feed speed or the feed distance of the peripheral flange portion of the fuel tank 2 by the electrode wheel 46 is accurately and real time grasped. As described above, under the situation where the feed speed of the peripheral flange portion 4 fluctuates every moment, control of the robot cannot be performed in time. Also, once the welding line deviates from the regular trajectory, it is not easy to quickly restore it to its original position, and errors due to control delay tend to accumulate, which tends to cause poor welding. There was a problem. An object of the present invention is to completely abandon the concept of the conventional welding jig copying mechanism using the welding jig and the concept of the feed control of the fuel tank 2 depending on the numerical control of the robot. The operator of the seam welding visually checks the welding line and mechanically replaces the work of sending the fuel tank 2, thereby creating expensive copying jigs and complex programs for robots, and troublesome teaching of robots. The object is to eliminate work and the like. [0010] The copying apparatus of the present invention focuses on the fact that the welding line formed by the electrode wheels can be controlled by adjusting the rotation of the fuel tank in the horizontal direction. This will be described with reference to FIGS. FIG. 1 shows an XY table 50 in which three horizontal plates 48a to 48c are vertically stacked, and the first and second plates 48a and 48 from the bottom.
b, the second and third plates 48b, 4 from the bottom
8c, the first and second linear guides 52, 52, respectively.
54 are provided. The first and second linear motion guides 52 and 54 enable the plates 48a to 48c to slide in a linear direction, and the lower first linear motion guide 52 and the upper second linear motion guide 54 are mutually connected. They are arranged orthogonally. That is, the first translation guide 52 is an X-direction translation guide, and the second translation guide 54 is a Y-direction translation guide. A copying control shaft 56 is provided on the upper or lower surface of the XY table 50. In FIG. 2, the XY table 5
It is assumed that the scanning control shaft 56 is provided on the lower surface of the zero.
The scanning control shaft 56 is a rotation shaft of a motor capable of precisely controlling a rotation angle, for example, a rotation shaft of a step motor or a servo motor. Then, it is considered that a work 58 to be welded in which two metal sheets are stacked is supported at the lower end of the copying control shaft 56. In such a state that the workpiece to be welded 58 is supported, the peripheral edge of the workpiece (corresponding to the peripheral flange 4 of the fuel tank) is sandwiched between the electrode wheels 46, and the electrode wheel 46 is rotated to seam weld the peripheral edge of the workpiece. . At this time, when the scanning control shaft 56 is rotated in either the forward or reverse direction, the direction of the workpiece 58 with respect to the electrode wheel 46 changes. When this is viewed from the electrode wheel 46 side, the traveling direction of the electrode wheel 46 has changed. FIG. 3 shows an example of the relationship between the rotation direction of the scanning control shaft 56 and the traveling direction of the electrode wheel 46. When the electrode wheel 46 is traveling along the linear portion of the peripheral portion of the workpiece 58 to be welded (see FIG. When the control axis is rotated clockwise in accordance with the point A), the electrode wheel 46 is shifted inside the workpiece 58 to be advanced. When the electrode wheel 46 approaches the corner, the scanning control shaft 56
Is adjusted clockwise by 90 °, the electrode wheel 46 makes a curve at 90 ° to the left in the traveling direction. This is the control principle of the welding line of the present invention. Although the conventional fuel tank 2 is supported by the iron man 14, the iron man 14 cannot support the rotational reaction force of the scanning control shaft 56, so that the XY table 50 as shown in FIG. Or a supporting means having a function equivalent to this is required. Plate 4
By arranging various known link mechanisms and universal joints between 8a to 48c, it is possible to realize a configuration that supports the work movably in the horizontal direction while supporting the rotational reaction force as in the XY table 50. . The above-described control of the welding line can be easily understood by imagining a cloth feeding operation by a sewing machine. The feed direction of the sewing machine is always straight, but the stitch direction is changed by turning the fabric horizontally and changing the angle of the fabric fed to the needle. The XY table according to the present invention provides a slip between the sewing machine table and the cloth at this time. Further, the function of the hand for turning the fabric corresponds to the copying control axis of the present invention. The welding line automatic copying apparatus according to the present invention is an application of the above-described welding line control principle. The welding line automatic copying apparatus according to the present invention employs the above-described welding line control principle. In an automatic copying apparatus for correcting a welding locus of an electrode wheel by adjusting a horizontal rotation of a work, a first linear guide and a second linear guide are disposed orthogonally to each other in two upper and lower gaps of a three-layer plate. of the XY table to permit movement of any horizontal direction while restraining the horizontal pivoting movement, superposed and scanning control shaft having a major axis in the vertical direction perpendicular to the movement allowable direction of the XY table, the XY One of the table and the scanning control axis is supported by the tip of the robot arm, and the other is
A dedicated jig for supporting a work having a portion to be seam-welded is mounted, and a template having the same or similar contour as a planned welding line of the work is mounted on the dedicated jig in alignment with the work, and a seam welding machine is provided. A reference member is fixedly arranged at a position facing the contour of the template in a vertical plane commonly including the axes of the pair of upper and lower electrode wheels, and a gap between the contour of the template and the reference member is detected. A distance sensor is provided, and control means for controlling the rotation of the scanning control shaft based on an output from the distance measuring sensor so that the gap distance is constant is provided. An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG.
8 of the articulated robot 74 fixed to the floor 72
A C-shaped frame 86 is attached to the tip of the second unit 2 via a scanning control shaft 84 and an XY table 50 as support means. The scanning control shaft 84 is a rotation shaft of a step motor or a servo motor capable of precisely controlling the rotation angle, and the terminal rotation shaft of the robot can be used as it is.
An XY table 50 is supported at the lower end of the scanning control shaft 84. The XY table 50 is the same as that described above, and the first plate 48c from the top
4 is fixed to the lower end. An exclusive jig 6 is fixed to the lower surface of the XY table 50, and the fuel tank 2 is positioned and fixed under the exclusive jig 6. A clamp 90 movable up and down by a cylinder 88 is provided at the lower end of the C-shaped frame 80.
The clamp 84 can press and fix the lower surface of the fuel tank 2. The XY table 50 can be replaced with another mechanism as long as it can move in any horizontal direction but restricts the movement in the horizontal turning direction. For example, as shown in FIG. A universal joint 76 is provided between the upper and lower plates 48d and 48e, or a parallel link mechanism 7 is provided between the upper and lower plates 48f and 48g as shown in FIG.
8 is disposed horizontally, one end 78a of the parallel link 78 is connected to the lower plate 48f, and the other end 78b is slidably engaged with the groove 80 formed on the lower surface of the upper plate 48g. It can be replaced. A template 92 is fixed on the upper part of the special jig 6 as shown in FIGS. The template 92 is formed of a plate having a substantially rectangular contour and a contour similar to the outline of the expected welding line of the peripheral flange portion 4 of the fuel tank 2, and is aligned with the fuel tank 2, that is, the corresponding sides are in the same direction. It is arranged horizontally so as to face. On the other hand, a fixed arm 94 extends downward from the main body of the seam welding machine 44, and a reference member 96 is attached to a lower end of the fixed arm 94. This reference member 96
Are located in a vertical plane including the axis of the pair of upper and lower electrode wheels 46 in common, and as shown in FIG.
Is opposed to the contour of In the vicinity of the reference member 96 at the tip of the fixed arm 94, a distance measuring sensor 98 is attached. The distance measuring sensor 98 measures a gap distance between the contour of the template 92 and the reference member 96. Next, control of the scanning control shaft 84 will be described.
When the peripheral flange portion 4 of the fuel tank 2 is seam-welded without rotating the scanning control shaft 84, the welding line is basically straight. Error cannot be corrected. When the front end of the welding line deviates from the scheduled welding line, the distance between the reference member 96 and the contour of the template 92 changes to either wide or narrow.
This is detected by the distance measuring sensor 98, and the scanning control shaft 84 is rotationally controlled so that the change in the width of the interval is restored. Further, welding of the corner portion of the peripheral flange portion 4 of the fuel tank 2 is also performed by rotation of the copying control shaft 84. That is, the electrode wheel 4
6 passes the welding start point at the corner, and at the same time, the distance between the contour of the template 92 and the reference member 96 increases.
The distance measuring sensor 98 continuously detects the degree of the spread of the interval, and the rotation of the scanning control shaft 84 is controlled by control means (not shown) so that the spread is restored. The scanning control shaft 84 can be controlled by means other than the above-described template 92, reference member 96 and distance measuring sensor 98. Generally, the planned seam welding line of the fuel tank 2 and the actual welding It suffices if there is a sensor for detecting a deviation from the front end of the line, and control means for controlling the rotation of the scanning control shaft 84 based on the output from this sensor so as to make the deviation zero. The distance measuring sensor 98 detects the distance between the template 92 and the reference member 96, which is equivalent to detecting the deviation between the scheduled seam welding line and the actual front end of the welding line. Therefore, a sensor that directly detects the position of the front end of the welding line of the fuel tank 2 can be used instead of the distance measuring sensor 98. Next, another embodiment of the present invention will be described with reference to FIG. The automatic seam welding line copying apparatus shown in FIG. 7 also uses the robot arm 82, and is basically the same as the above-described embodiment, except that the XY table 50 and the dedicated jig 6 or the template 92 The difference is that the tool changer 100 is provided. The tool changer 100 has a shaft 102 protruding from the dedicated jig 6 side detachably locked by a spring 103 and a steel ball 104 as shown in an enlarged sectional view. When the tool 6 is to be replaced, the steel ball 104 is retracted by vacuum so that the shaft 102 can be easily removed. By using the tool changer 100, versatility can be provided from the robot arm 82 to the XY table 50, which is effective in reducing equipment costs or shortening the cycle time when there are many types of fuel tanks 2. It is a target.
In FIG. 7, reference numeral 106 denotes a knurl roller and reference numeral 108 denotes a cutting tool. The other parts substantially the same as those in FIGS. 4 and 5 are denoted by the same reference numerals. Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, the scanning control axis 8
4 is arranged on the upper side, and the XY table 50 is arranged on the lower side. Conversely, the XY table 50 is arranged on the upper side, and the scanning control shaft 84 is arranged on the lower side. May be. As described above, according to the present invention, the direction in which the welding line is formed on the work is controlled only by the rotation of the scanning control shaft, so that the conventional expensive copying jig or robot can be used. There is no need for complicated programs at all, and a great rationalization effect can be achieved. In addition, since the supporting means is supported by the tip of the robot arm, most of the moving range of the work is covered by the movement of the robot arm, so that the supporting means can be reduced in size. This is particularly large in seam welding of a large work. It will be an advantage.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an XY table. FIG. 2 is a perspective view showing a relationship between a welding wheel and a scanning control shaft. FIG. 3 is a plan view of a workpiece showing welding line copying control. 4A is a perspective view of a robot and an automatic seam welding line copying apparatus, FIG. 4B is an enlarged perspective view of the seam welding line automatic copying apparatus, and FIG. 4C is a side view of a template and a distance measuring sensor. FIG. 5A is a side view of an automatic seam welding line copying apparatus,
(B) is a top view of an automatic seam welding line copying apparatus. FIG. 6A is a side view showing a modification of the support means,
(B) is a perspective view showing still another modification of the support means. FIG. 7 is a perspective view of a seam welding line automatic copying apparatus according to another embodiment of the present invention. FIG. 8 is a side view of a conventional welding line scanning control device. FIG. 9 is a plan view of a fuel tank. 10A is a perspective view of a rail, FIG. 10B is a plan view of a front end of the rail, and FIG. 10C is a longitudinal sectional view of a rear end of the rail. [Description of Signs] 2 Fuel tank 6 Special jig 44 Seam welder 46 Electrode wheel 50 XY table 74 Articulated robot 82 Arm 84 Copying control axis 90 Clamp 92 Template 96 Reference member 98 Distance measuring sensor ΔL

Continuation of the front page (56) References JP-A-62-230488 (JP, A) JP-A-7-241684 (JP, A) JP-A-62-13274 (JP, A) JP-A-6-91380 (JP, A) , A) Japanese Utility Model 62-155972 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 11/06 101 B23K 11/06 520 B23K 11/24 350 B25J 9/06

Claims (1)

(57) [Claim 1] Correction of the welding locus of the electrode wheel at the peripheral portion of the workpiece when the peripheral portion of the workpiece is sandwiched between a pair of upper and lower electrode wheels by seam welding is performed by adjusting the horizontal turning of the workpiece. In the automatic copying apparatus to be performed, a first linear guide and a second linear guide are disposed orthogonally to each other in two upper and lower gaps of a three-layer plate, and the horizontal movement direction of the work is restricted in an arbitrary horizontal direction. And a scanning control axis having a main axis in a direction orthogonal to the movement allowable direction of the XY table are vertically overlapped with each other, and one of the XY table and the scanning control axis is moved to the tip of the robot arm. A special jig for supporting a work having a portion to be seam-welded is attached to the other, and a balance having the same or similar contour as a line to be welded to the work is attached. The base member is fixed to the dedicated jig in alignment with the work, and the reference member is fixed at a position in a vertical plane including the axes of the upper and lower electrode rings of the seam welding machine in common and facing the contour of the template. The distance measurement sensor that detects the gap distance between the contour of the template and the reference member is arranged,
A seam welding line automatic copying apparatus, further comprising control means for controlling rotation of the copying control shaft so that the gap distance is constant based on an output from the distance measuring sensor.